As daughter of the former demon lord, Mio's foster parents were slain by powerful demons after her life. Still seeking to slay her, Basara reveals himself as a member of the hero clan--an enemy of the demons--and vows to protect Mio as a member of his family.
I'd like you and Mio-sama to form 
a Master-Servant testament.
Ich möchte, dass du und Mio-sama
ein Meister-Diener-Testament besiegeln.
Quiero que formen un pacto 
entre maestro y siervo.
Quiero que forméis un pacto 
entre maestro y siervo.
Je voudrais que tu deviennes
le vassal de maîtresse Mio.
Vorrei che tu e Mio-sama stipulaste
 un contratto Servo-Padrone.
Eu gostaria que você e a Mio-Sama 
fizessem um pacto entre Mestre e Servo.
Я хочу, чтобы госпожа Мио заключила 
с тобой договор господин-слуга.